reactos/hal/halppc/generic/fmutex.c

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/*
* COPYRIGHT: See COPYING in the top level directory
* PROJECT: ReactOS HAL
* FILE: hal/halppc/generic/fmutex.c
* PURPOSE: Deprecated HAL Fast Mutex
* PROGRAMMERS: Alex Ionescu (alex@relsoft.net)
*/
/*
* NOTE: Even HAL itself has #defines to use the Exi* APIs inside NTOSKRNL.
* These are only exported here for compatibility with really old
* drivers. Also note that in theory, these can be made much faster
* by using assembly and inlining all the operations, including
* raising and lowering irql.
*/
/* INCLUDES *****************************************************************/
#include <hal.h>
#define NDEBUG
#include <debug.h>
#undef ExAcquireFastMutex
#undef ExReleaseFastMutex
/* FUNCTIONS *****************************************************************/
VOID
FASTCALL
ExAcquireFastMutex(PFAST_MUTEX FastMutex)
{
KIRQL OldIrql;
/* Raise IRQL to APC */
KeRaiseIrql(APC_LEVEL, &OldIrql);
/* Decrease the count */
if (InterlockedDecrement(&FastMutex->Count))
{
/* Someone is still holding it, use slow path */
FastMutex->Contention++;
KeWaitForSingleObject(&FastMutex->Event,
WrExecutive,
KernelMode,
FALSE,
NULL);
}
/* Set the owner and IRQL */
FastMutex->Owner = KeGetCurrentThread();
FastMutex->OldIrql = OldIrql;
}
VOID
FASTCALL
ExReleaseFastMutex(PFAST_MUTEX FastMutex)
{
KIRQL OldIrql;
/* Erase the owner */
FastMutex->Owner = (PVOID)1;
OldIrql = FastMutex->OldIrql;
/* Increase the count */
if (InterlockedIncrement(&FastMutex->Count) <= 0)
{
/* Someone was waiting for it, signal the waiter */
KeSetEventBoostPriority(&FastMutex->Event, IO_NO_INCREMENT);
}
/* Lower IRQL back */
KeLowerIrql(OldIrql);
}
BOOLEAN
FASTCALL
ExiTryToAcquireFastMutex(PFAST_MUTEX FastMutex)
{
KIRQL OldIrql;
/* Raise to APC_LEVEL */
KeRaiseIrql(APC_LEVEL, &OldIrql);
/* Check if we can quickly acquire it */
if (InterlockedCompareExchange(&FastMutex->Count, 0, 1) == 1)
{
/* We have, set us as owners */
FastMutex->Owner = KeGetCurrentThread();
FastMutex->OldIrql = OldIrql;
return TRUE;
}
else
{
/* Acquire attempt failed */
KeLowerIrql(OldIrql);
return FALSE;
}
}
/* EOF */